In construction work, such as the carpentery involved in framing building structures, there is frequently a need for marking angle lines on members to be cut. In many situations the precise angle necessary is not readily determined and it is desirable to replicate an angle which has been assumed by another member already in place. This task may be done in a various ways using a variety of implements of the prior art. Each implement for tasks such as this, and a variety of other similar angle-marking tasks, is referred to herein as an angle guide apparatus.
Many different angle guides for this sort of purpose have been disclosed in the prior art. Some examples of such prior art devices include those disclosed in the following United States patents:
U.S. Pat. No. 596,818 (Moore) PA0 U.S. Pat. No. 1,086,545 (Meister et al.) PA0 U.S. Pat. No. 1,806,396 (Hartwell) PA0 U.S. Pat. No. 1,908,518 (Lee) PA0 U.S. Pat. No. 2,878,569 (Metrulis) PA0 U.S. Pat. No. 3,522,657 (Metrulis) PA0 U.S. Pat. No. 4,144,650 (Rawlings et al.) PA0 U.S. Pat. No. 4,194,295 (Simuro et al.)
As can be seen readily, certain devices of the prior art include a main member with a main straight edge, a bubble-level device attached to the main member, and an angle arm with a proximal end pivotably attached to a proximal end of the main member, such angle arm having its own straight edge. Many different arrangements and structures have been used in such devices. Some have protractor elements useful for setting a predetermined angle. Others have spring and flat-spot arrangements which facilitate setting to certain predetermined angles. In one the angle arm may be fixed at any position by certain adjustments which require tools such as a screwdriver.
Each of the devices of the prior art of this general type has problems or disadvantages for the most common uses.
In some cases adjustment and readjustment of the angle between the angle arm and the main member is quite difficult, such adjustment requiring steps which are time-consuming and which require a number of manipulations. Such difficulties of operation can cause misadjustment of the angle, that is, a failure to properly replicate the angle to be replicated.
With certain other devices of the prior art operation may be particularly problematic when the devices are used in a symmetrical reverse-angle marking, that is, when duplicate angles which are symmetrical reversals of each other must be marked. In many such cases, a visual alignment of the main-member straight edge may be necessary for at least one of the symmetrical angle markings, and this can result in questionable reliability in the markings.
Some devices of the prior art are relatively weak and flimsy in construction to the extent that the degree of accuracy of markings can be compromised. This is contrary to the intended purpose of such devices. Yet, in very rigid constructions adjustment and readjustment of the angle, or, more specifically, releasably holding the angle at the chosen position, has required excessive manipulative steps with the attendant disadvantages.
A number of devices of the prior art are of complex and expensive construction. There is a clear need for an improved angle guide apparatus for convenient and easy replication of angles, both for direct and symmetrical reverse-angle markings, in construction operations and the like.